As is known, microfluidic systems are being used in an increasing number of applications, including biological applications. In order to perform these applications, microfluidic systems must carry out various types of functions such as sample purification, separation and detection. These functions, in turn, require the development of various microfluidic components such as filters, valves and detectors and the incorporation of the components into an integrated microfluidic system.
A typical detector consists of a sensor to test the sample within the microenvironment of a microfluidic device and a display unit to present the results of such test. In order to detect and monitor the environment inside these micron-sized devices, several sensitive methods have been contemplated including conductivity measurement, UV-visible spectroscopy and fluorescence spectroscopy. It can be appreciated that such methods are usually associated with complex instrumentation thereby making fabrication of the corresponding microfluidic systems difficult. In addition, operating such complex instrumentation often requires significant power, and hence, utilization of power sources such as batteries or the like. These power sources may be considerably larger than the microfluidic device itself, rendering the microfluidic system too heavy or too large to be attractive to potential users.
For certain applications like evaluating the purity of water or finding the pH range for a sample of fluid, detecting the existence of a change is more important than the extent of the change. Further, in other applications, the precise quantitative results may not be as important as the rapid detection ability and/or the portability of the system. For example, quickly obtaining the results from a pregnancy or diabetes test may be more important to a user than the precise quantitative results.
Therefore, it is a primary object and feature of the present invention to provide an apparatus for sensing changes in the micro-environment within a microfluidic device that does not require utilization of power sources such as batteries or the like.
It is a further object and feature of the present invention to provide a method and apparatus for monitoring the environment within a microfluidic device that quickly detects the change of the environment within the microfluidic device.
It is a still further object and feature of the present invention to provide a method and apparatus for monitoring the environment within a microfluidic device that is simple and inexpensive.
In accordance with the present invention, a microfluidic device is provided for displaying indicia in response to a change in the predetermined parameter of a fluid flowing therethrough. The microfluidic device includes a body member defining a channel accommodating the flow of the fluid therethrough. A monitor structure is proposed in the channel of the body in the flow of fluid. The monitor structure displays a first indicia in response to a predetermined parameter of the fluid having the first value and a second indicia in response to the predetermined parameter of the fluid having a second value.
The monitor structure includes a polymerized mixture. The polymerized mixture includes an immobilized dye which is a first color in response to the predetermined parameter of the fluid having the first value and which is a second color in response to the predetermined value of the fluid having the second value. It is contemplated that the first indicia displayed by the monitor structure is provided by the dye being the first color and the second indicia displayed the monitor structure is provided by the dye being the second color. The dye may be phenolphthalein or congo red.
The mixture may include a hydrogel, a photoinitiator and a cross-linker. It is contemplated that the polymerized mixture have a first dimension in response to the predetermined parameter of the fluid having the first value and a second dimension in response to the predetermined parameter of the fluid having a second value. In such circumstances, the first indicia displayed by the monitor structure is provided by the polymerized mixture being the first dimension and the second indicia displayed by the monitor structure is provided by the polymerized mixture being the second dimension.
The microfluidic device may also include a second monitor structure disposed in the channel of the body in the flow of fluid. The second monitoring structure provides a first indicia in response to a second predetermined parameter of the fluid having a first value and second indicia in response to the second predetermined parameter of the fluid having a second value.
In accordance with a further aspect of the present invention, a method is provided for monitoring an environment within a microfluidic device. The method includes the steps of providing a monitor structure in a channel of the microfluidic device and passing fluid over the monitor structure in the channel. The monitor structure generates a visual display in response to exposure to a parameter of the fluid having a predetermined value.
In order to provide the monitor structure, a dye is immobilized in a polymer matrix. This is provided by mixing the dye in a prepolymer mixture and providing the same as a pregel. The pregel is injected in the channel and polymerized in the channel to form the monitor structure. Thereafter, the channel of the microfluidic device is cleaned.
The pre-polymer mixture includes a hydrogel, photo-initiator and a cross-linker. More specifically, the pre-polymer mixture may 2-hydroxy ethyl methacrylate (HEMA), acrylic acid (AA), ethylene glycol dimethacrylate (EGDMA), and 2,2-dimethoxy-2-phenylacetophenone (DMPA). The dye may be phenolphthalein or congo red.
The method of the present invention may also include the additional steps of providing a second monitor structure in the microfluidic device and passing fluid over the second monitor structure in the channel. The second monitor structure generates a visual display in response to exposure to the second parameter of the fluid having a predetermined value.
In accordance with a still further aspect of the present invention, a method is provided for monitoring the environment within a microfluidic device. The method includes the steps of mixing a dye in a pre-polymer mixture and providing the same as a pregel. The pregel is injected into a channel of the microfluidic device and polymerized therein to form a monitoring structure. The fluid is passed over the monitoring structure in the channel such that the dye changes color in response to the parameter of the fluid having the predetermined value. When the pregel is polymerized within the channel, the dye is immobilized in the polymerized mixture. The dye may be phenolphthalein or congo red. The pre-polymer mixture may include a hydrogel, a photo-initiator and a cross-linker. More specifically, the pre-polymer mixture may include 2-hydroxy ethyl methacrylate (HEMA), acrylic acid (AA), ethylene glycol dimethacrylate (EGDMA), and 2,2-dimethoxy-2-phenylacetophenone (DMPA).
It is contemplated that the monitor structure change dimension in response to the predetermined value of the second parameter of the fluid. In addition, a second monitor structure may be provided in the channel. Fluid is passed over the second monitor structure such that the second monitor structure changes color in response to a second parameter of the fluid having a predetermined value. The second monitor structure may be fabricated by mixing a second dye in a second pre-polymer mixture and providing the same as a second pregel. The second pregel is injected into the channel of the microfluidic device and polymerized therein so as to form the second monitor structure. After the first and second pregels are polymerized in the channel, the channel of the microfluidic device is cleaned.